Keyword Basics Part 1: How search engines use keywords

In this article we look at exactly how search engines use keywords, examining both on-page and off-page factors. Read on to see the full list of keyword metrics.

Keywords are most important when it comes to determining relevance - the connection between the search terms and the results. Unless a page is relevant to the search term it won't rank at all. Making a page more relevant can increase rankings and is often where you'll find some of the best quick wins for gains in rankings. Below I go through all the ranking factors in which keywords play a role. If you're interested in learning how exactly to apply these you should check out my article all about how to optimise a web page.

On-page keywords

These are some of the most established ranking factors and often what we think of in terms of ‘traditional’ SEO. Don’t be fooled into thinking that makes them any less relevant. Ignore these at your peril and your search result may sink without trace...

Page title

Keywords in the page title are one of the oldest and most prominent ranking factors. Keyword placement within the title is also important. Make sure your keywords appear at the beginning to give them additional weight.


Another older metric, page headings are still worth optimising. Make sure your main keywords for the page are in your <h1> tags. Use the other heading tags for variations on your keywords and closely related terms.

Frequency in content

The number of times you use keywords in content is important. Make sure your main keywords appear at least once, with closely matching terms being used throughout.

LSI keywords in content

Don’t just use your primary and secondary keywords and think you’re done. Google is looking for the content as a whole to match the search terms. This means making sure you have keywords closely related to the search term throughout the content.


Optimise your image alt, title tags and filenames. Make sure these include your keywords or closely related terms. Also bear in mind alt tags are used by screen readers as well, so these need to be actually descriptive of the image for accessibility.

Keyword prominence in content

Use your main keywords within the first 100 words of content. This shows these are the focus of the content, increasing relevance.

Outbound links

The pages you link to and the anchor text you use to do so is also important. Keywords should be included within the anchor text, and the content you're linking to needs to be related to your main keywords for the page.


Make sure your main keywords are within the URL for the page. Google will often shorten URLs in the search results to the domain and the page.

Page category

If it’s a content page, then it may well be in a category within your site. The actual category and subcategory a page is in also counts towards relevance. Having your keywords or closely related terms appear in the category names adds to relevance.


Exact match domains may not carry the weight they previously did, but it’s still a strong signal the domain and page within it are highly relevant. Just watch out for domain names which are too long or sound spammy. These will weaken your brand and ultimately damage rankings.


Off-page factors can have even more weight than on-page. They are harder to manipulate and show Google what the general consensus on your page is, rathen than just what you say it is.

Anchor text

This is one of the most important ranking factors. Relevant anchor text shows that other sites deem the content relevant as well. Beware the over optimisation of anchor text, as this will create a negative ranking signal and certainly damage your rankings.

Internal link anchor text

It’s not just the anchor text from external links, but internal ones as well which count. Use your keywords within the internal links, especially those that appear in your site's navigation.

Linking domain relevance

The domain that links to you is obviously important from a link value perspective, but also from the point of view of relevance. If the domain is relevant to your keywords then that's going to increase the relevance of the linked page to those terms.

Linking page relevance

The relevance of the page as a whole and the text which surrounds the links is really important. This shows the links are in context, making them pass more relevance to the target page.


This is the correlation between a page and the targeted keywords from content across the web. Where the a site is frequently mentioned alongside a set of keywords, even if it’s not linked, this indicates a connection between the two.

Social Media as a ranking signal

The keywords you use in social media matter - for your social media campaigns. They don't however directly affect your SEO rankings. Here's Matt Cutts (Google's head of Webspam) to explain more.

If you want to know more about social signals and SEO you can check out my full write up on the problems with using social as a ranking factor.


This is not a complete list of ranking factors, there is tons more stuff to consider. These are just the keyword specific metrics. If you want to learn more about SEO then check out our Academy articles and guides.

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Keyword Basics

For the rest of our Keyword Basics series:

Keyword Basics Part 2: Finding keywords

Keyword Basics Part 3: Understanding a keyword's structure

Keyword Basics Part 4: Targeting your primary and secondary keywords

Keyword Basics Part 5: How to narrow down your keyword list

Keyword Basics Part 6: Keyword mapping

Keyword Basics Part 7: Using keyword modifiers

Keyword Basics Part 8: Building keyword rich inbound links